Windows can account for 10% to 25% of your heating bill. During the summer, sunny windows make your air conditioner work two to three times harder. If your home has single-pane windows (almost half of U.S. homes do), consider replacing them.
Reflective Window Film:Reflects up to 50% of incoming solar heat and 90% of UV radiation light. Decreases cooling costs in the summer. For the average 1,600-2,000 sq. ft. home, it only takes 18-24 months to pay back your initial investment in the film, which has a lifetime of about 15 years. Not recommended for south-facing windows if your goal is solar heating.
Cost: 50¢ to $1.20 per sq. ft.
High-Efficiency Windows: Each single-paned window in your home is akin to having a 6" circular hole installed in your wall. If you have single-paned, aluminum framed windows, you can reduce your heating and cooling costs from 15% to 60% percent, by upgrading to Energy Star double-paned windows.